Piston grinding machine



4 Sheets-Sheet 1 Filed March 51, 1949 Inventor Cm/e lvc JGREEN By M w'ttorneg C. J. GREEN PISTON GRINDING MACHINE June 1( 1952 4 Sheets-Sheet 2 Filed March 31, 1949 II II III Inventor Cm/ema JG/EEE/Y 3 um.

Httorrzgy June 10, 1952 c. J. GREEN PISTON GRINDING MACHINE Filed March 31, 1949 4 Sheets-Sheet 3 [7a 219 72 to r CLHKE/YCE JGEf/EN 3 Mo. ea,

J 10, 1952 c. J. GREEN PISTON GRINDING MACHINE 4 Sheets-Sheet 4 Filed March 31, 1949 fizz/enter CLFIRE/YCE LIG/ZEE/Y Patented June 10, 1952 PISTON GRINDING MACHINE Clarence J. Green, Worcester, Mass., assignor to Norton Company, Worcester, Mass., a. corporation of Massachusetts Application March 31, 1949, Serial No. 84,659 8 Claims. (01. 51-101) The invention relates to grinding machines and more particularly to a grinding machine for grinding irregular shapes such as elliptical or oval surfaces on pistons and the like.

One object of the invention is to provide a simple and thoroughly practical grinding machine for grinding an oval or elliptical shape on an automotive piston. Another object of the invention is to provide a piston grinding machine with a master cam and follower roller which are arranged to produce a tapered oval or elliptical shape on a work piece. Another object of the invention is to provide a cam type machine for gen erating a predetermined tapered contour on the periphery of a piston. A further object of the invention is to provide a piston grinding machine having a pivotally mounted rock bar which is oscillated during a grinding operation by means of a master cam and follower roller to support one end of a work piece to be ground while the other end is rotatably supported on a fixed axis to facilitate generating an irregular shape which tapers from one end to the other. Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, and arrangements of parts, as will be exemplified in the structure to be hereinafter described, and the'scope of the application of which will be indicated in the following claims.

I In the accompanying drawings in which is shown one of various possible embodiments of the mechanical features of this invention:

Fig. 1 is a front elevation of a grinding machine embodying the invention;

Fig. 2 is a fragmentary plan view of the machine, on an enlarged scale, showing the work supporting and driving mechanism;

Fig. 3 is a sectional view taken approximately on the line 3-3 of Fig. 2, showing the work driving mechanism;

Fig. 4' is a sectional view taken approximately on the line 4-4 of Fig. 2, showing a portion of the work driving mechanism;

Fig. 5 is a. fragmentary horizontal sectional view, on an enlarged scale, showing the work supporting arrangement together with the master cam and follower roller; 4

Fig. 6 is a fragmetary cross sectional view, on an enlarged scale, taken approximately on the line 6-6 of Fig. 2, showing the pivotal support for the footstock;

Fig. 7 is a cross sectional view, taken approximately on the line 'I--I of Fig. 5, showing a por- 2 tion of the work supporting and driving device in end elevation;

Fig. 8 is a diagrammatic showing of the essential parts of the machine;

Fig. 9 is an elevation, on an enlarged scale, of the ground portion of the work piece;

Fig. 10 is a left hand end elevation of Fig, 9 showing the shape of the ground work piece; and

Fig. 11 is a diagrammatic view showing the arrangement of the parts set up for grinding tapered ovals on pistons being ground, tapering in either direction.

A grinding machine has been illustrated in the drawings comprising a base III which supports a longitudinally movable work table I I on the usual flat and V-ways (not shown) The table I I serves as a support for a cam grinding unit I2 which will be hereinafter described. The table I I may be reciprocated longitudinally relative to the base I0 to facilitate positioning the work piece being ground for a grinding operation by means of a manually operable traverse mechanism comprising a traverse wheel I3. The traverse wheel I3 is connected to rotate a gear I4 which meshes with a gear I5 mounted on a rotatable shaft I6. The shaft I6 also supports a gear I! which meshes with a rack bar I8 depending from the underside of the work table II. It will be readily apparent from the foregoing disclosure that a manual ro-' tation of the traverse wheel I3 will be imparted through the rack and gear mechanism above described to produce a longitudinal traversing movement of the table II. The direction of rotation of the traverse wheel I3 serves to determine the direction of movement of the table I I. This mechanism is substantially the same as that disclosed in the prior United States patent to C. H. Norton, No. 762,838, dated June 14, 1904, to which reference may be had for details of disclosure not contained herein.

The table II, if desired, may be reciprocated longitudinally by a power operated mechanism such as that shown in the prior patent above referred to. This mechanism may comprise a rotatable power driven shaft I9 which is driven by means of a multiple speed drive contained within a casing 20. The rotatable shaft I9 is connected through a reversing clutch (not shown) which is actuated by means of a reversing lever 2|. The reversing lever 2| is actuated by a pair of adjustable table dogs 22 and 23 which are adjustably supported in a T-slot 24 formed in the front edge of the table II.

A rotatable grinding wheel 25 is mountedon.

one end of a rotatable wheel spindle 26. The

3 wheel spindle is journalled in spindle bearings (not shown) supported within a transversely movable wheel slide 21. The wheel slide 21 is arranged to be adjusted transversely on the usual flat and V-ways (not shown) formed on the base ID. The grinding wheel 25 may be driven by any suitable means, such as for example, a motor 28 mounted on the upper surface of the wheel slide 27. The motor is provided with an armature shaft 29 which is connected by a multiple V-belt drive (not shown) contained within a belt guard A manually operable feed wheel 3 l is mounted on the front of the machine base i8 and is op eratively connected to rotate a feed screw (not shown) to cause the grinding wheel 25 and the wheel slide 21 to move transversely toward or from the work table il, depending upon the direction of rotation of the feed wheel 33. In the construction illustrated in the drawings, the feed wheel 3| may be actuated either manually or automatically as desired. A mechanically actuated feed pawl 32, such as that shown-in the prior patent above referred to, is reciprocated automatically to advance the grinding wheel -25 at the ends of the 'reciprocatory stroke of the table II.

A cam grinding unit [2 comprises a frame '35 which is clamped to the upper surface of-the work table I I. The frame serves as a support for a rock bar 33. The rock bar 38 is provided at its opposite ends with a pair of spaced axially aligned trunnions 31 and 38 which are supported by a pair of spaced bearing brackets 39 and '48 respectively; The bearing brackets 39 and, Ml are fixedly mounted on the frame 35. A headstock unit 4! to be hereinafter described is provided with a work supporting center 42 which-is arranged to engage and support one end of a piston 43 to be ground.

The piston 43 to be ground is supported at its left hand end by means of a work holder 45 having a recess 45 adapted to receive the left hand end of the piston 43 (Fig. 5). The work holder 45 is provided with pivotally mounted clamping jaws 41, 48 and 49 which are actuated by adjust ing screws 50, 5! and 52 respectively. As illustrated in Figs. 5 and 7, the clamping jaws 41, "48 and49- are arranged to engageone of the grooves formed in the periphery of the piston 43 being.

ground to hold the piston rigidly in position on the work holder 45. A center hole 53 is provided on the work holder 45 which is arranged to be supported by the center ,42. The: workholder 135 is provided with a pair of spaced driving lugs 54 and 54a (Figs. 5 and 7). The headstock center- 42 is mounted on the right hand end of a rotatable master cam spindle 55. The master cam spindle 55 also supports a driving plate '55 having a driving pin 51 fixedly mounted thereon. The driving pin 51 is arranged to project between the lugs 54 and 54a. The lugs 54 and-54aare provided with opposed aligned adjustingscrews 58 and 580, which are arranged to engage opposite sides of the driving pin 57. By adjusting the screws 55 and 58a, the timing or positioning of the piston being ground may be adju'st'ed relative to the master cam to be hereinafter described.

In the grinding of automotive pistons such as some of the aluminum alloy and other alloy pistons, it is desirable to grind a relief on the sides of the piston adjacent to the thi'ckened'bo'ss portions 88 and 85 (Figs. 5 and 9) due to the factthat when the pistonbecom'es heated {durright hand end of the piston 43 (Fig. 5) toward the left hand end thereof. In other words the right hand-end of the piston 43 (Fig. 5) may be substantially cylindrical and this surface then tapers on the axis CD toward the left (Fig. 5)

to vproduce a desired relief on the axis CD passing through the hub portions 88 and 89 (Figs. 5 and 9), so as to compensate for greater expansion at this point due to heating of the piston in normal use.

In order to accomplish the desired result, a footstock 6llis provided having a footstock spindle 6| which supports a self-aligning anti-friction bearing 62. The bearingEZ serves as a support for a work holder 63 (Fig. 5) which is arranged to engage a recess '64 formed within the right hand end of the piston 43. In order to facilitate grinding the above described complex shape on the piston 43, the footstock 531s preferably mounted independent of the rock bar-.35. As illustrated in the drawings, a rock shaft 55 is fixedly mounted at its left hand end in the bracket 48. The right hand end of the rock shaft 65 is supported by a bracket 63 which is mounted on the table H. The footstock 55 is supported on the rock shaft and is arranged to be clamped in adjusted position thereon by means of clamping screws '61 (Fig. 6).

The master cam spindle 55 is supported in spaced aligned bearings Ill and 'H which are in turn supported by the rock bar 36. The master cam spindle 55 supports a master cam' 12. which is shaped to generate a predetermined contour'on the work piece as will be hereinafter described.

A suitable driving mechanism is provided for the master cam spindle 55 comprising a universal joint 13 (Figs. 2 and 4) which connects the master c'am spindle 55 with a rotatable shaft .14. A universal joint i5 serves to drivingly connect the shaft I4 with a multiple V-groove pulley 1-6 which is supported by anti-friction bearings Ti. An electric motor I8 is supported by a bracket 39 on the ,table' II. The motor 13 is providedwi'th an armature shaft 60' which is connected .to rotate a worm 8| (Fig.3). 7 The worm 8! meshes with a worm gear 82 which is keyed on a rotatable shaf-t' '83. A gear .84 is also keyed on the shaft 83 and meshes with a gear 85 which is keyedon a rotatable clutchmemb'er 83. The clutch member 86 isrotatably supported on a shaft 81'.

It is desirableto provide-for a multiple speed of the'piston 43 being ground. This is preferably accomplished by'providing a second gear train comprising a gear 88 keyed on the left hand end of the shaft 83. The gear H5 meshe with a gear IIB. which is keyed on a rotatable clutch member 90. The clutch. member 90 is also rotatably supported on the shaft ST. A slidably mounted clutch member 9! is provided which'is keyed on the shaft 81 and is arranged so'th'at it may be shifted longitudinally relative thereto by means of a manually operable lever 92 into engagement with either the clutch member 186 14 and the master cam spindle 55 to rotate the piston 43 being. ground. v

A master cam follower roller 95 is mounted on a rotatable shaft 96 which is carried by a pair of spaced brackets 91 and 98 formed integral with the headstock unit 4 I.

A suitable mechanism is provided for yieldinglymaintaining the master cam I2 in operative engagement with the follower roller 95'duringa grinding operation. This mechanism may'comprise a tension spring I which'is connected at one end by a stud IOI with a bracket I02 (Fig. 8). The bracket I02 isfixedly mounted by'means of screws I03 on the rock bar 38. The other end of the spring I00 is provided with a'stud I04 which passes through a hole or aperture I05 in the'casing I05 of the headstock unit 4 I. The right hand end of the stud I04 is provided with a threaded portion I01 which is engaged by a nut I08. It will be readily apparent from the foregoing disclosure that by adjustment of the nut I08, the tension of the spring 90 may be varied as desired to maintain the master. cam I2 in operative engagement with the'master. cam roller 95 with the desired pressure during a grinding operation.

It is desirable to provide a suitable mechanism for separating the master cam 72 from the follower roller 95 to facilitate removing the ground piston 43 from the machine and replacing it with a new piston to be ground. This mechanism may comprise'a manually operable lever I I0 (Figs. 1 and 8) which is mounted on the outer end of a rock shaft III. A cam II2.is fixedly mounted onthe inner end of the rock shaft III (Fig. 6). The cam H2 is arranged in the path of an adiustably mounted stud I I3 carried by the bracket I02. When it is desired to separate the master cam,I2 from the follower roller 95, the lever IIO may be rocked in a clockwise direction (Fig. 1) so that the cam H2 will move into engagement with the stud II3 after which continued movement of the lever H0 and the cam II2 serves to rock the rock bar 36 in a counterclockwise direction (Fig. 8) so as to separate the master cam I2 from the follower roller 95.

In-order to generate the desired shape on the piston 43, it; is desirable to support the piston in the work holder 45 so that when positioned in the machine as illustrated in Fig. 5, the transverse axis of the piston passing through the wrist pin bosses 88 and 89 will correspond with the short axisof the oval or ellipse formed on the master cam 72. This is preferably accomplished by providing a special fixture (not shown) by which the operator may'locate the piston on the holder 45 in a definite position with relation to the lugs 54 and 54a and the driving screws 58 and 58a. After the piston has been thus located, the clamping jaws 41, 48 and 49 areswung into engagement with one of the grooves on th piston 43 and the screws 50, 5| and 52 are adjusted to clamp the piston 43 rigidly in position on the holder .45. The holder 45 together with the piston 43 are then positioned in themachine with the centerhole 53 of the work holder engaging the headstock center 42 and the work holder 63 is moved. into. supporting engagement with the: recess 64 formed inthe open end of the piston 43..

The master cam 12 1s then positioned so that one end'of its long'axis, that is'the long axis of the oval or ellipse formed thereon, is in engagement with the master cam follower roller 95. With the parts in this position, the footstock 50 'is rotarily adjusted on the shaft 65 (Figs. 2 and 6) so that the axis of the footstock spindle 6| is aligned with the axis of the master cam spindle 55. After this adjustment hasbeen made,-the clamping screws 61 are actuated to lock the footstock 50 in adjusted position. The driving screws 58 and 58a are then adjusted rotarily to adjust the position of the work holder so that a transverse axis of the piston at right angles to the bosses 88 and 89 is positioned in a horizontal In this position the rock bar is plane (Fig. 2). in its extreme position rocked away from the grinding wheel and when the machine is started by the work driving motor 18', the rock bar will be rocked to oscillate the left hand end of the piston 43 during rotation thereof so as to generate a complex surface thereof in which an oval shape is produced which varies from a maximum relief at the left handend to a minimum or zero relief at the right hand end of the piston 43. Due-to the setup of the machine as above described, the axis of the piston being ground will be rocked from its left hand end during rotation thereof so that the oval" or ellipse generated thereon will have the minor axis aligned with the axis of the wrist pin bosses 88 and 89. With this condition,

a given size piston, it only becomes necessary.

to withdraw one of the screws 58 or'58a after a grinding operation has been completed to remove It will be readily apparent from the foregoing disclosure that at diametrically opposite positions of the piston 43 being ground the axis of the footstock spindle BI and the axis of the master cam spindle 55 will be aligned. As the master cam spindle 55 rotates, the master cam I2 will cause the rock bar to oscillate so that the Work holder 45 and the left hand end of the piston 43 will be oscillated toward and from the periphery of the grinding wheel while the axis of the footstock spindle 6| maintains the axis of the work holder 53 in a relatively fixed position. This arrangement is diagrammatically illustrated in Fig. 11 which shows the master cam spindle 55 together with the piston 43 and the footstock spindle 8I as positioned in extreme positions, namely when the master cam I2 is positioned to engage the follower roller on its long and short axes.

The tapered oval shape generated on the piston center 42 and the aligning axis of the self- 7x aligning anti-friction hearing .62. This .may be accomplished-by providing longeror shorter work holders-63 on the footstockend. 'If a work holder 631$;pXlOVidGdWhiChLiS short enough so that the right hand: end; of the piston 43 (Fig. 5) is in theplane. or the aligning; axisof the .bean'ng'63',. then ansubstantially cylindrical surface will be generated on the-piston at the right hand :end. Inthis-case the relief willstaper from asubstantiallytruev cylinder to: an oval. as governed:..by the master cam, 12 and theposition of .the:.lefthand. end .of the piston lid-relative toxthe headstookpenter. 42:. The worksholder'. (l5 may the; similarly varied in length. for positioning. the left hand end. of the piston ,43 relative to. the headstock center 42. :It willbe readily apparent fromthe foregoing disclosure that, by providing longer .or shorter 'workholders ,163- and .45, the

shape of the relief ground, upon :the periphery of the skirt of the piston Ailmay be varied as desired. As shown in- Figure 51 :and" diagrammatically in Fig. .11., .th'enright hand end-ofthe piston .-43.-.-is spaced from the axis of support .on

the footstock end so that a slight relief will be produced on the right hand end of the piston 43 which-will increase toward the left due to the wabbling motion transmitted to the left hand end of the piston 43 by-the master cam 12 which causes-arocking movement of the rock bar towardand from the grinding wheelld during rotation ofthe piston 43 being ground.

As shown in Figs. 5 and. 1.1, the machine is set up with the axis of the footstock spindle 61 adjusted into alignment with the axis of (the master cam spindle 55 when the high point of the master cam 12 is in engagement withthe master cam roller .95- so=that a taperedoval shape is generated on the piston tapering fromtherighthand end of the piston (Figs. 5 and 11) toward the left.

It maybe desirable to grindthepistonin the reverse manner, namely to mount thelopen .end of thepiston on the headstock center .42 in which case the taper on the piston will .taper from the open end of the piston toward theright asfshown diagrammatically in Fig. 1.1. In this condition of the parts, the footstock. 50 is adjustedon its supporting shaft so thatthe axisof thefootstoek spindle is alignedwith the axis of the master cam spindle55 when the lowpoint o'f-the master cam 12 is in operative. engagement with the master cam roller 12. In this application, of the invention the master cam 12 would have to be generated to meet the reverse conditionof operation.

In the first described method of operation the footstock spindle '61 is aligned with the axis of the master cam spindle 55' when the master cam spindle is positioned in broken line position; "55a Fig. 11) and the master cam 12a is'positi'oned withthehigh point of the master cam 12 in operativeengagement with the master cam roller 9.5. As themaster cam. spindle is rotated to retate :themaster cam .11 and the pistons being ground, the footstock end. of the-spindle showndiagrammatically in Fig. 11 will rotate about the axis of the footstock spindle .5 while rotation of the master cam 12 will cause the rock bar 36 to rock the master ,eam spindle" .from .position ESalFig. 11) to full line position :55 togenerate a tapered oval shape on the piston 43 as illustrated in broken lines 43a fiFig. 11) .in which .the tapered oval tapers from .the right hand fiend ofthe piston toward-the left.

ilnxthe reversesetup.abovezdeseribedrthemaster 8 cam spindle is positioned in position. iiwiwithathe low'pointof the master cam 12 in engagement with the follower roller. 95. In this. positiomiof' the partsathe footstock BB is adjusted .so thatithe axis ofthe footstock spindle .61 is .alignedvwith the axis of the: .masterrcam spindle. 55 in posttion-15511.. When themaster cam spindle flies-is rotated, the rotation thereof will be transmitted to rotate the piston 43 aboutrthez axis of the-.rfootstock spindle 6|? while the master: cam 12a: will cause the rock zbar 36 and the master camspindle: 55am rock towardtheposition SS'baCEig. lll tha't is it will rock the left hand end: of- .the pistorrA-Su: away from the grinding. Wheel-50171131; a: tapered surface' will-be produced onthe peripheryirof :the: piston ,as illustrated diagrammatically in brokenlines-43bv tapering from thelefthandend: tlnarleioztv toward. theright. If the. latter? arrangement of partseis utilized the work holderrfi'may' he..elim-- inatedzand a-specialrelativelylargeconical;center: be provided: in place of the headstock center #2 This. special driving: center will engag the: .opert end of the piston and .be "provided with .a' driving-f lug. which; projects withinithe hollowpiston; and drivingly engages .one'xof. the inwardly projecting wristlpin bosses Biland 89;

The operation of this improved grindingma chine wilhbe" readily apparent from; the foregoing.

disclosure. Assumingalllof the partsfto havezlieeir previously adjusted and a master cam 12 .afjlthe desired mantour. .igxmounted 0n the: master. .cam spindleii, aworkpiecesuchas apiston ilillwhich has been previously locatedzas above described onrthe :work holder 45 is mounted imposition in supporting:engagementmitlithe headstock center" 42 and' thework holder .53 carried: .by .the .'foot-- stock 6.0;. .As above described on.the initial.grinding: operation; th v driving screws i58aaudl 58a1are: adddstedrtdlocate the axis of the piston passing throughnthe .axis of the-wrist pin' bosses .88 and 89' in a predetermined relationship with-Ithe mastercam. 12. The grinding operation may thenzproceed land the grinding wheel may: be advanced by actuation of: the feed wheel-3| to grind. the desired and predetermined shape on the periphery .of the piston. 43. After ithe piston has :been: groundto-the predetermined sizeand contour; the maehine may :be stoppedand one :of the screws 58 01- 5811. loosened to facilitate removaleof the workpiece from the machine. .It is of course necessary to move the footstock spindle 6| towardthe-right (Figsszand 5) towithdraw the work holder-'63 from the recess 64 after theground' piston. and the worhiholderflfi may be removed from themaprovidingamaster oam ..l2=o the .desiredishape,

any desiredamount of relief may be groundso'n th pistonaxisqpassing. throughithe'axisnf wristipinihossesa88and;

:It willithus beseerrpthat there :has been..;;pro-

\ videdby inventionapparatusin which the various objects hereinabove .set :forth together with..:many thoroughly practical advantages are successfully-achieved. Asmanypossiblexemhbdimerits-may :bezmade of gthe :above invention and asmany-ohangesmight 'bermade .inthe embodt ment above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings i to be interpreted as illustrative and not in a limiting sense.

I claim: v

1. In a piston grinding machine having a transversely movable rotatable grinding wheel, a work table, a rock bar pivotally supported on said table, a rotatable master camspindle on said rock bar, means including a master cam on said spindle and a follower roller to impart a rocking movement to said rock bar, means including a work supporting center onsaid spindle to support one end of a work piece to be ground, a pivotally mounted footstock on said table having a longitudinally adjustable spindle, a self-aligning workholder on said spindle to support the other end of the work piece, and means to adjust said footstock transversely so that its spindle axis is aligned with the axis of the master cam spindle when a high point of the master cam is in engagement with the follower roller so that the-end of the work piece adjacent to the footstock rotates about a substantially fixed axis whil the other end of the work piece rotates with the master cam spindle and is rocked toward-and from the grinding wheel as controlled by the master cam to generate a variable relief on the work piece being ground.

2. In a piston grinding machine having a rotatable grinding wheel, a work table, a rock bar pivotally supported on said table, a master cam spindle on said rock bar, means including a master cam on said spindle and a rotatable follower roller on said table to impart a controlled rocking movement to said rock bar when the spindle is rotated, means including a work supporting center on said spindle to support one end of a work piece to be ground, a pivotally mounted footstock, a pivotal support for the footstock on said table, a self-aligning workholder carried by the footstock for rotatably supporting the other end of the work piece, and means to adjust said footstock on its pivotal support so that its axis is aligned with the axis of the master cam spindle when the high point of the master cam is in engagement with the follower roller so that the end of the work piece adjacent to the footstock rotates about a substantially fixed axis while the other end of the work piece is rotated and wobbled as controlled by rotation of the master cam spindle and the master cam to generate a tapered contour on the work piece.

3. In a piston grinding machine having a transversely movable rotatable grinding wheel, a longitudinally movable work table, a rock bar pivotally supported on said table, a rotatable master cam spindle on said rock bar, means including an oval-shaped master cam on said spindle and a rotatable follower roller on said table, means including a workholder supported by said spindle to support one end of a piston to be ground, a pivotally mounted footstock having a spindle, the pivotal axis of the footstock being axially aligned with the pivotal axis of the rock bar, a self-aligning rotatable workholder on said footstock spindle to support the other end of the piston to be ground, means pivotally to adjust the footstock so that the axis of the spindle is aligned with the axis of the master cam spindle when a high point of the master cam is in engagement with the follower roller so that rotation of the master cam spindle will impart a rotary revolving movement to one end of the piston as controlled by the master cam while the other end of the piston is rotated by a substantially fixed -10 axis to generate a tapered oval shape on the piston being ground.

4. In a piston grinding machine having a transversely movable rotatable grinding wheel, a work table, a rock bar pivotally supported on said table.

a rotatable master cam spindle on said rock bar,

means including a master cam on said spindle and a follower roller to impart a controlled rocking'movement to said rock bar during rotation of said spindle, a workholder supported by said spindle to support one end of a work piece to be ground, a footstock pivotally mounted on said table, and means to adjust the footstock about its pivotal axis so that the footstock spindle may be positioned in axial alignment with the axis of the master cam spindle when a high point of the master cam is in engagement with the follower roller so that one end of the work piece to be ground rotates about a substantially fixed axis while the other end of the piston rotates and revolves with the master cam spindle as it isrocked by the master cam so as to generate a predetermined tapered shape on the work piece being ground. I

5. In a piston grinding machine having a transversely movable rotatable grinding wheel. a longitudinally movable work table, a rock bar pivotally supported on said table, a rotatable master cam spindle on said rockbar which is arranged parallel to the axis of the rock bar, means including 'an oval-shapedmaster cam on said spindle and a follower roller on said table, means including a work supporting center on said spindle to support one end of :a work piece to be ground, a pivotally mounted footstock on said table, the pivotal support for said footstock being axially aligned with the pivotal axis of the rock bar, a spindle on said footstock which is arranged parallel to the pivotal support of the axis of the rock bar and spaced therefrom by a distance equal to the spacing of the master cam spindle from said axis, and means to adjust the footstock about its axis so that the footstock spindle may be positioned in axia1 alignment with the axis of the master cam spindle when a high point of the master cam is in engagement with the follower roller so that one end of the piston being around rotates about a substantially fixed aXis of the footstock spindle while the other end of the piston rotates with the master cam spindle and is rocked toward and from the grinding wheel as controlled by the master cam to generate a tapered oval shape on the piston being ground.

6. In a piston grinding machine having a transversely movable rotatable grinding wheel, a work table, a rock bar pivotally supported on said table, a rotatable master cam spindle on said rock bar, means including a master cam on said spindle and a follower roller to impart a rocking movement to said rock bar, means including a work supporting center on said spindle to support one end of a work piece to be ground, a pivotally mounted footstock on said table having a footstock spindle to support the other end of the work piece, and means to adjust said footstock about its pivot so that the axis of the footstock spindle is aligned with the axis of the master cam spindle when a low point of the master cam is in engagement with the follower roller so that the end of the work piece adjacent to the footstock work-table, a rock bar pivotallysupported.onsaid tabl a rotatable master cam'spindle on said roek bar; means including-a master cam onsaid spindle and afollower 'roller'to impart-a eontrolled-aocking movement tosaid rock-barduring rotation ofsaid spindle; a workholder'supported by -said spindle to support one end of a: work piece to be-g round, a footstock-pivotally mounted on-saidfitable and means to adjust the -footstocl: aboutits pivotal-axis sq {that the footstock spindle may be positioned in axial alignment with the axis of the master cam spindle whenalow point of tlieniaster cam is in'engagernentwitlrtl e lollower rollerso that one end of thevworkwpieee to be grou-nd rotates about a substantially fixeqlaxis whilef the other 'end ofthe piston roltates ancl revoltes with the master cam spindle as itisrooked by. the master cam-so asto generateapredeter mined taperedflshape on the work piecebeing ground. v V

8. In a piston grinding machine I having; a

transversely. movable rotatablegrindingrwheel a longitudinally movable Work= table, aw'roelgbar piyotally' supported on said table a rotatable master cam spindle on said-rock bar whiohvis arranged parallel to the! axis of th'e rook bar. means includingan oval-shaped master. cain on saidlspindle and a followeriroll'er on said table, means including a Work supportingcente'r, onfsaid spindle to smpportone end. of a workpiece to be 12 ground a: pi-yotallyz" mountec1==-footstocl =ro1rrsaid table: thapivotal support -fon=saidfifootstoek-being axially: alignedrwith the pivotal taxisot ltherrook bar, a spindle-ons aid footstock wh-ich is arranged parallel to the pivotal support of the axis of the rock bar and: spaced therefrom: by9a: distance equal to the spacing of the master; cam spind1e from said axis, and means toadjust the-rootstock about its 'axisso :th-atthefootstock: spindle may be positionedin axial alignment witl'r the axisof the master: cam spindle'when a-wlowpoint-.ofjhe master camisin-engagementtwith: theafollower roller? so thatone end of; the piston being;galound rotates about a; substantially fixed. axisiof the footstook spindle whilethe other end of thelpiston rdtates the master cam spindle andl-is rockedawaly-ifroin andtoward; thefgrinding; wheel; as controlled by the master eam torgenerate a-ta- I pered oval shape -on-the piston beingagrounm CLARENCE-P5P GREEN? REFERENGES rcrrnn Tlieiollowing e n-e1ices" are bf rec'b'rd -nritfie file -'of this' patent? 

